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Seeing as XTR cranks have a 24mm spindle you might as well go for normal BB threads as you will not get the full benefits of BB30 but you will possibly get the hassle of regular bearing replacements and creaks. To me BB30 and PF30 are not an advancement at all.

You could use a BB92 cups but really whats wrong with BSA threads. They have worked fine for years. Go with BB92 if you worry about how stiff your cranks are. If you do worry about that then you really should find something else to worry about.

I suppose one deciding factor would be is a BB92 shell more expensive than a BSA shell.

My Form Prevail Ti 29er I got with a PF30 BB, and my latest Ti bike I was going to go that way also. But then I was convinced by the builder to go with BSA 73mm. I've heard all the arguments about this better than that... but what settled it for me was two things:1) Ease of working on: if something is wrong with your PF30 BB, eg creaking, or binding, etc then good luck servicing it. You'll probably destroy the cups of the BB in trying to remove it (assuming it was loctited in place as it needs to be to not creak). With BSA its obviously very easy2) Bearing stance: on the PF30 bike I have hollowgram cranks and the bearings are 73mm outside to outside. On the BSA bike I also have hollowgram cranks, installed with a Rotor BB and the bearings are 73mm inside to inside. That's a significant increase in bearing stance that should make the cranks stiffer and the bearings last longer.

I had a Moots RSL with a PF30 bb. I must say that I did not love the PF30- too many issues with bearings, creaking, etc. If I were to get another ti hardtail I would get a threaded bb and put a King bb in it- done.

I think BB92 or BB386 would be idea. That way you can keep the BB as wide as possible so you can optimize the downtube and seatstays for stiffness. The weld area could be bigger as you can work the Ti tubes to have the right shape factor at the weld area.

BB30 is still a narrow bottom bracket shell. PF30 is the same.

BB92, or BB386 is where it starts really getting wider and get really optimized.

I've seen quite a few ti frames with downright awful bb shell tolerance issues. like over 1mm variance in shell width at different points, non-round pf30 bores with up to 0.5mm interference, etc. Larger spindles are less tolerant of misalignment than smaller ones. Some shops won't ream/face ti frames as they're hard on cutting tools, and most don't have the tools to do it to a nonthreaded frame.whichever you choose, make sure they properly finish it.

This is the exact reason I'm on the fence about replacing my current MTB (Ti Litespeed Niota) most of the current ti offerings are all PF30 and after riding with a good friend on a Moots with a PF30 I don't want to deal with the non-stop creaking/squeeking.

At NAHBS I talked about this for a while with the builder from Mosaic. He was a proponent of using a BB30 shell (not PF30) with the Rotor BB adapter to 24mm cranks. He liked this because the Rotor BB cups thread together and pull the BB in tight... which prevents creaking he said and allows you to remove and service the BB with simple tools. Praxis make a similar BB I think for PF30 frames. Only downside is that they marry you to 24mm spindle cranks.

I tend to agree with you (see my earlier post). Mosaic seemed to think that the BB30 shell is a "nicer platform to build around". He felt like there were perceived stiffness payoffs with the frame. I'm skeptical myself, but I mention this in the context of people who are anxious about not having a choice by PF30, or who already have a PF30 frame.